It is either that or may have been caused by mistake while moving to other dat.

That could be a probable cause, however no other dats containing "CPR" exist, so either it was a mistake or there's a very good reason for the removal. Perhaps the maintainer will see this post and let us know...

OK Cassiel, i've decided your answer is a bit confusing, to me at least. I was not aware of the specs/history of the GX4000. From what i've read, it's "based on the CPC+ series" so i'm guessing that since the GX4000 is basically a CPC6128+, its dats should contain only files released specifically for it. AFAIK, everything that is compatible with the CPC 464 is also compatible with the 6128. The + is another story, so if those CPRs are also playable on the plain CPC (that's my interpretation of duplicate), shouldn't they exist in the CPC dats and not in the GX dats? After all, everything playable in the CPC should be also playable in the GX but not vice versa.

I guess the bottom line is if the GX is basically a CPC6128+ and the 6128+ supported files are in the CPC dats, why have a special dat for the GX? Why not have separate dats for the CPC+ series (at least the files not playable by a plain CPC) instead?